The U.S. Constitution establishes three eligibility requirements for service in the Senate: age, citizenship, and residence. At the beginning of the 20th century, a Senate committee voted to add one more qualification—religion.

At issue was whether Utah Republican Reed Smoot—a Mormon—should be allowed to serve. Soon after the Utah legislature elected the influential banker early in 1903, the Senate received a petition protesting his seating. A group of Protestant ministers and businessmen opposed to Mormon economic policies particularly feared Smoot, who at age 40 had risen to his church's powerful Quorum of Twelve Apostles.

The Senate seated its new member subject to an investigation. Soon, senators were deluged with thousands of petitions from Protestant churches, women's groups, and others outraged by the Mormon faith's association with polygamy. The writers charged that the church leadership held supreme authority over temporal, as well as spiritual, matters for its members and frequently interfered in Utah politics. They also complained that the leaders continued to encourage polygamy, even though the church had officially terminated its practice years earlier. Smoot was the third child of his father's fifth wife, but not himself a polygamist.

In 1904, the Senate launched its investigation to determine whether Smoot had taken a church oath that included "an obligation of hostility to the United States." The inquiry quickly expanded beyond Senator Smoot to become a full dissection of the church's structure and machinery. The investigation consumed two years. Its report filled five thick volumes.

On June 1, 1906, despite overwhelming evidence that none of the practices of Smoot's church had any bearing on his fitness for Senate service, the committee narrowly recommended that he be removed from office.

A bright moment in this otherwise ugly episode came in a floor speech by the committee's ranking majority member, who testified that Smoot stood out among his colleagues for having no vices. "He does not drink, or smoke, or chew, or swear."

On February 20, 1907, the Senate brought Smoot's three-year ordeal to a close, voting 43 to 27 that he should keep his seat. The Utah Republican went on to serve an illustrious 30-year Senate career, including 10 years as chairman of the Finance Committee. In that capacity, he co-authored the 1930 Smoot-Hawley Tariff. To his dismay, that highly protectionist measure worsened the Great Depression and cost him his seat in the resulting 1932 Democratic landslide.

Reed Smoot died in 1941 at age 79, one step removed from the presidency of his church.